Communications system and communications apparatus

ABSTRACT

A communications system configured to execute data transmission between a transponder having no radio wave generating source thereof and a reader/writer is provided. The communications system includes, a service permission level notifier configured to tell a service permission level for associated with a received signal level for permitting service acceptance from the reader/writer to the transponder, and an access controller configured to determine in the transponder whether the received signal level from the reader/writer is at the notified service permission level to determine accessibility to the transponder from the reader/writer.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/112,804, filed Apr. 30, 2008, which claims priority to JapanesePatent Application JP 2007-136282 filed in the Japanese Patent Office onMay 23, 2007, the entire contents of which is being incorporated hereinby reference.

BACKGROUND

The present disclosure relates to a communications system of noncontacttype in which a communications terminal (or a transponder) containing noradio generating source transmits data with a device (or areader/writer) that is a communications mate in a wireless manner and toa communications apparatus that is configured to operate as atransponder or a reader/writer in the communications system. Moreparticularly, the present disclosure relates to a communications systemand a communications apparatus that are configured to execute datacommunication on the basis of reflected-wave transmitting by use of thetransmission of a non-modulated carrier from a reflected-wave reader andthe absorption and reflection of received radio waves based on aterminal operation at an antenna of a reflector.

In detail, the present disclosure relates to a communications system anda communications apparatus that are configured to execute datacommunication between a transponder and a reader/writer that arearranged at an optimum communications distance and, more particularly,to a communications system and a communications apparatus that areconfigured to execute communication at an optimum communicationsdistance for every application between the transponder and thereader/writer and, at the same time, prevent the interception by nearbycommunications terminals so as to ensure the security of transmissiondata.

A noncontact communications system called RFID (Radio FrequencyIdentification) is known as a communications system that is configuredto transmit data by radio without having an own radio generating source.The RFID is also referred to as an ID system and a data carrier system.Commonly used worldwide is an RFID system or simply RFID, a recognitionsystem based on high frequency (radio). The RFID system is made up of atransponder called a tag and a reader/writer for accessing thetransponder. The transponder passively operates on the radio suppliedfrom the reader/writer as an energy source and the reader/writer readsinformation from the transponder and writes information thereto.

The noncontact communications methods based on the RFID includeelectrostatic coupling, electromagnetic induction, and radiocommunicating, for example. With the RFID system based on radiocommunicating, the transponder has a reflector configured to transmitdata by a reflected wave obtained by modulating a non-modulated carrierand the reader/writer has a reflected-wave reader configured to readdata from a modulation reflected-wave signal received from thereflector, thereby executing reflected-wave transmission also calledbackscatter. Receiving a non-modulated carrier from the reflected-wavereader, the reflector modulates the reflected wave on the basis ofantenna load impedance switching for example, thereby superimposing dataonto the carrier. Namely, because the reflector requires no carriergenerating source, a data transmission operation can be driven at lowpower dissipation. The reflected-wave reader receives the modulatedreflected wave thus obtained and demodulates and decodes the receivedwave to obtain transmission data.

Basically, the reflector has an antenna for reflecting radio that is anincident continuous wave, transmission data generating circuit, and animpedance variation circuit for varying a load impedance of the antennain correspondence with transmission data (Disclosed in Japanese PatentLaid-open No. Hei 1-182782). The impedance variation circuit is anantenna switch for switching between open and ground of the terminal ofthe antenna, for example. This antenna switch may be made up of a CMOS(Complementary Metal Oxide Semiconductor) transistor by building theantenna switch into a circuit module. It is also practicable toconfigure the antenna switch by a GaAs (Gallium Arsenide) IC (IntegratedCircuit), separate from the circuit module, thereby realizing high-speedswitching at low power dissipation. In the latter, a data transmissionrate based on reflected-wave modulation is enhanced, while the powerdissipation is suppressed below several 10 μW. Therefore, considering apower dissipation of about sever hundred mW to several W in a wirelessLAN (Local Area Network), the reflected-wave communication can be saidto be remarkably higher in performance than the average powerdissipation of a general LAN (Disclosed in Japanese Patent Laid-open No.2005-64822).

Because the transponder carrying a reflector only executes an operationof reflecting received radio, the transponder is not regarded as a radiostation, so that this transponder can be advantageously handled asoutside the regulations imposed on radio communication. Whileconventional noncontact communications systems use frequencies ofseveral MHz to several hundred MHz (13.56 MHz for example), thereflected-wave transmitting can use a high-frequency band of 2.4 GHz(microwave) called ISM (Industry Science and Medical Band), for example,thereby realizing high-speed data transmission.

In one typical exemplary use of a noncontact communications system, ahost device incorporating a transponder, such as a reflector, isarranged on the reading surface of a reader/writer, such as areflected-wave reader as shown in FIG. 8, thereby executing informationreading and writing on the transponder.

The transponder can obtain an electrical power by rectifying a carriertransmitted from the reader/writer; but this power is not enough for thetransmission of large amounts of data at high frequencies. Namely, withthe transponder, an electrical power for generating a carrier at thetime of transmission is not required, while an electrical powernecessary for a transmitting operation for modulating a reflected waveand a receiving operation for demodulating and decoding a modulatedsignal from the reader/writer is supplied from the host device.

For example, if the transponder is built in portable informationterminals, such as a digital camera and a mobile phone with camera and amobile terminal device, such as a portable music player, which areminimized in power dissipation and the reader/writer is built ininformation equipment based on stationary household appliances, such asa television set, a display monitor, a printer, a personal computer(PC), and a VTR (Video Tape Recorder), a DVD (Digital Versatile Disc)player, then bringing the transponder and the reader/write to proximityof each other allows uploading of image data taken by a mobile phonewith camera or a digital camera to the PC in a noncontact manner,thereby storing, displaying, or printing the uploaded image data.

A memory card having capabilities of transponder, such as a reflector,is proposed (disclosed in Japanese Patent Laid-open No. 2006-216011).Such a host device loaded with such a memory card as a digital camera ora mobile phone can access the loaded memory card via a wired interface.On the other hand, an external device, such as a PC or a printer, canread data from a loaded memory card via a reflected-wave transmissionroute independently of the host device loaded with the memory card.Namely, a noncontact communications operation can be controlled out ofcontrol of the host device loaded with a memory card, so that hostdevice need not install any driver software necessary for controllingnoncontact communication since the memory card connects to an externaldevice.

Data transmission between transponder and reader/writer requires toestablish connection therebetween. For one of communicationsestablishing procedures, a service entry sequence is proposed in whichthe reader/writer transmits a beacon frame at certain intervals to tella service area of own station. (For example, see Japanese PatentApplication No. 2006-270365 which has been already devolved to theapplicant of the present disclosure)

FIG. 9 shows a communications control sequence for executingreflected-wave transmission between transponder and reader/writer by useof the above-mentioned service entry sequence.

The reader/writer periodically transmits a beacon frame to tell theservice area of own station. Also, in an entry period to be providedafter the transmission of a beacon frame, the reader/writer continues totransmit a non-modulated carrier for operating the transponder.

On the other hand, the transponder receives a beacon frame to know theexistence of the reader/writer and uses the non-modulated carrierreceived within the entry period to return an entry frame in response tothe received beacon frame.

FIG. 10 shows a sequence in which a communications operation is startedbetween reader/writer and transponder by use of the service entrysequence shown in FIG. 9.

The reader/writer executes the transmission of beacon frames at certaintime intervals in an intermittent manner. The transponder cannot receivebeacon frames outside a radio reach range. However, when the transponderachieves in the radio reach range and a beacon frame comes, thetransponder executes the processing of receiving the beacon frame.

On the basis of the information written to the payload of the receivedbeacon frame, the transponder obtains information about communicationsfrequency channels to be used and information such as the ID unique tothe reader/writer. In order to establish connection with thereader/writer, the transponder returns an entry frame composed ofmodulated reflected-wave signal in an entry period by use of anon-modulated carrier transmitted from the reader/writer describedabove.

On the basis of the written contents of the entry frame transmitted fromthe transponder, the reader/writer obtains the information such as theID unique to the transponder and communications parameters that can beset. In order to make communication with the transponder, thereader/writer transmits a connection request frame with specifiedinformation such as communications parameters written to the payload. Inresponse to this connection request, the transponder returns aconnection response frame with the information such as a connectionresult written to the payload, upon which the connection betweentransponder and reader/writer is established. While the connection isestablished, information is read from the transponder and writtenthereto by repeating the transmission of command frames from thereader/writer and the return of response frames by the transponder.

The reader/writer need not always continue to transmit beacon frames atcertain time intervals. For example, the reader/writer can establishconnection through the same connection request/response sequence asdescribed above after the transmission of a beacon frame (or anirregular transmission request signal) when to read information from thetransponder (to be more specific, every time an application forreading/writing data with the transponder is started up). Namely, thereader/writer can suppress the transmission of unnecessary beacon framesand the transmission of the non-modulated carrier during an entryperiod.

In the communications sequence shown in FIG. 10, a handshake is executedbetween the reader/writer and the transponder by use of a beacon frameand entry frame and then the reader/writer transmits a connectionrequest frame, in response to which the transponder returns a connectionresponse frame. Conversely, it is also practicable for the transponderto transmit a connection request frame, in response to which thereader/writer returns a connection response frame.

Today, a noncontact communications system, such as described above,executes an information read/write operation in a noncontact mannerbetween the transponder and the reader/writer, thereby enhancing theconvenience of use to expand the application of this system to theconventional magnetic cards, such as commuter passes and certificationcards, and distribution systems.

Unlike wired communication, wireless communication is much morevulnerable to the risk of the interception of information that iscarried by wireless communications systems, so that the communicationroutes must be encrypted. For example, if the non-contact communicationssystem is used for the reading/writing of value information, such as thesettlement in electronic money, or room access control, the ability ofcommunication with terminals located in the proximity of the transponderand the reader/writer presents a serious problem in security.

For example, with wireless LAN systems, such as the IEEE 802.11 system,a scheme is introduced in which encryption keys, such as WEP (WiredEquivalent Privacy) and PSK (Pre-Shared Key) are held in common in theBSS (Basic Service Set) managed by a control station, thereby enablingthe terminal stations accommodated in a network to have securecommunications paths based on encryption. However, the installation ofsuch a scheme on noncontact communication systems that are characterizedby low-cost configuration is not realistic.

With noncontact communications systems based on electromagneticinduction, the induction field decreases in inverse proportion to thecube of distance, so that the risk of interception by nearbycommunications terminals is comparatively low. However, withapplications in which the transponder is installed on a device providingan information source, such as a digital camera, a mobile phone withcamera, or a portable music player, to transmit information content tothe reader/writer of a display apparatus or an audio output apparatusfor outputting image or sound, it is inconvenient to have thecommunications distance limited to proximity

The noncontact communication based on reflected-wave transmitting usesradio waves that attenuate in reverse proportion to distance, so thatthe communications distance is comparatively long for enhanceduser-friendliness, but at the cost of sufficient security measures forthe transmission of value information.

SUMMARY

Therefore, the embodiments of the present disclosure address theabove-identified and other problems associated with related-art methodsand apparatuses and solves the addressed problems by providing acommunications system capable of suitably executing noncontact datatransmission between a transponder having no radio wave generatingsource of its own and a reader/writer and a communications apparatuscapable of suitably operating as a transponder or a reader/writer in theabove-mentioned communications system.

Another embodiment provides a communications system capable ofnoncontact data transmission based on reflected-wave transmitting and acommunications apparatus capable of suitably operating as a transponderor a reader/writer in the above-mentioned communications system.

Still another embodiment provides a communications system and acommunications apparatus that are configured to suitably execute datacommunication between a transponder and a reader/writer arranged at anoptimum distance.

Yet another embodiment provides a communications system and acommunications apparatus that are configured to execute communication atan optimum distance between a transponder and a reader/writer for everyapplication and, at the same time, keep the security of transmissiondata by preventing the interception by nearby communications terminals.

In carrying one embodiment thereof, there is provided a communicationssystem configured to execute data transmission between a transponderhaving no radio wave generating source thereof and a reader/writer. Theabove-mentioned communications system has a service permission levelnotifier configured to tell a service permission level for associatedwith a received signal level for permitting service acceptance from thereader/writer to the transponder; and an access controller configured todetermine in the transponder whether the received signal level from thereader/writer is at the notified service permission level to determineaccessibility to the transponder from the reader/writer.

It should be noted that term “system” as used herein denotes a logicalset of a plurality of component units and these component units are notnecessary accommodated in a same housing.

Because a noncontact communications system executes an informationread/write operation in a noncontact manner between the transponder andthe reader/writer, thereby enhancing the convenience of use to expandthe application of this system to the conventional magnetic cards, suchas commuter passes and certification cards, and distribution systems.

For example, compared with electromagnetic induction and the like,noncontact communications systems based on reflected-wave modulatingusing electric wave communication can increase the communicationsdistance for realizing high-speed data transmission using a highfrequency band of 2.4 GHz for example, thereby enhancing userfriendliness.

However, unlike wired communication, wireless communication is much morevulnerable to the risk of the interception of information that iscarried by wireless communications systems, so that applications forreading/writing value information such as the settlement by electronicmoney and room access control must be secured. On the other hand, if thecommunications distance is limited to proximity, user friendliness isdeteriorated in such applications as entertainment in which images takenby a digital camera are displayed on the television set, for example.

In contrast, the communications system according to an embodiment ismade up of a transponder and a reader/writer by applying noncontactcommunication such as reflected-wave transmission, for example, in whichthe reader/writer side controls the area communicable with thetransponder for each application. Therefore, user friendliness can beenhanced by limiting the communicable area with those applications whichrequire security such as the transmission of value information, whileenlarging the communicable area for entertainment applications.

The communications system according to an embodiment uses a serviceentry sequence (refer to FIGS. 9 and 10) in which the reader/writernotifies the transponder of a beacon frame at a predetermined timeinterval and the transponder returns a response frame in response to thebeacon frame by use of a predetermined entry period provided aftertransmission of the beacon frame, for example.

The reader/writer sets a service permission level in accordance with anapplication for providing a service to the transponder and notifies thetransponder of the set service permission level by means of a beaconframe. In response, the transponder determines whether a received signallevel of the beacon frame (or another received frame) received from thereader/writer is at the service permission level given by thereader/writer, thereby determining the accessibility to the transponderfrom the reader/writer.

Consequently, by setting a service permission level according to anapplication for providing service to the transponder, the reader/writercan control the area communicable with the transponder in accordancewith each application for providing a service to the transponder.

For example, if the reader/writer has started up an application forexecuting data communication of high security, the reader/writer sets ahigh service permission level to transmit a beacon frame. If the beaconreceived signal level is high, or the reader/writer is in the proximity,the transponder permits access from the reader/writer, therebypreventing interception by nearby communications terminals.

On the other hand, if the reader/writer has started up an applicationfor executing data communication, such as image or audio data requiringlow security, there is little need for caring about interception.Therefore, the reader/writer sets a low service permission level totransmit a beacon frame and, in response, the transponder permits accessby the reader/writer when the beacon received signal level is low, orthe communication distance with the reader/writer is comparatively long,so that the user need not bring the reader/writer and the transponderclosest to each other, thereby enhancing the ease of use.

As described and according to an embodiment, an excellent communicationssystem capable of suitably executing noncontact data transmission basedon reflected-wave transmission between a transponder having no radiowave generating source of its own and a reader/writer and an excellentcommunications apparatus capable of suitably operating as thetransponder or the reader/writer in this communications system areprovided.

In addition, an embodiment provides an excellent communications systemand an excellent communications apparatus that are capable of executingcommunication at a distance that is optimum for each application betweenthe transponder and the reader/writer and, at the same time, keeping thesecurity of transmitted data by preventing the interception by nearbycommunications terminals.

With the communications system according to an embodiment, theread/writer side controls the area communicable with the transponder foreach application. For example, the embodiment is applicable to acommunications system using “service entry sequence” (refer to FIGS. 9and 10) in which the reader/writer transmits a beacon frame to tell aservice area of its own and the transponder return an entry frame withina predetermined entry period. Having started up an application forreading/writing data with the transponder, the reader/writer sets aservice permission level according to the application (or a typethereof) and writes the set service permission level to the beaconframe. Having received this beacon frame, the transponder interprets thecontents of the received beacon frame and determines whether thereceived signal level of this beacon frame is at the service permissionlevel to determine the accessibility to the transponder from thereader/writer. Therefore, user friendliness can be enhanced by limitingthe communicable area with those applications which require securitysuch as the transmission of value information, while enlarging thecommunicable area for entertainment applications.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram illustrating an exemplary configuration ofa communications system practiced as one embodiment;

FIG. 2 is a block diagram illustrating an exemplary internalconfiguration of a memory card in which a transponder is incorporated;

FIG. 3 is a circuit diagram illustrating an exemplary internalconfiguration of a radio section in the memory card shown in FIG. 2;

FIG. 4 is a block diagram schematically illustrating an exemplaryinternal configuration of a reader/writer that functions as areflected-wave reader with which the radio section shown in FIG. 3communicates;

FIG. 5 is a diagram illustrating an exemplary frame format of a beaconsignal that is used in the communications system according to anembodiment;

FIG. 6 is a circuit diagram illustrating an exemplary configuration ofthe radio section having means of transmitting RSSI measurement resultsto a memory/communications control section;

FIG. 7 is a sequence chart indicative of an exemplary communicationssequence to be executed between a transponder and a reader/writer in thecommunications system according to an embodiment;

FIG. 8 is a perspective view of a host device incorporating atransponder such as a reflector arranged on a reading surface of areader/writer such as a reflected-wave reader, thereby executing areading/writing operation with the transponder;

FIG. 9 is a sequence chart indicative of a communications controlsequence for executing reflected-wave transmission between a transponderand a reader/writer by use of a service entry sequence; and

FIG. 10 is a sequence chart indicative of a sequence to be executed whenstarting a communications operation by use of the service entry sequenceshown in FIG. 9 between a reader/writer and a transponder.

DETAILED DESCRIPTION

Referring to FIG. 1, there is schematically shown a communicationssystem according to one embodiment. The communications system shown ismade up of a memory card 100 incorporating a transponder, not shown, ahost device 120 with this memory card 100 loaded in a dedicated slotthereof, and a reader/writer 300 configured to execute noncontact datatransmission with the transponder. The host device 120 may be a mobiledevice configured to accommodate the memory card 100, such as a digitalcamera or a mobile phone with camera. The transponder passively operateson a radio wave energy supplied from the reader/writer 300. Thereader/writer 300 reads information stored in the transponder and writesinformation thereto.

Noncontact communications methods include electrostatic coupling,electromagnetic induction, and radio communicating, for example. In whatfollows, the application of radio communicating is assumed, therebyexecuting reflected-wave transmission called backscatter. Thereflected-wave communicating is characterized by a low power dissipationin a communications form in which the transmission from the reflectorside occupies most of communication.

The transponder has a reflector configured to transmit data by areflected wave obtained by modulating a non-modulated carrier. Thereader/writer 300 has a reflected-wave reader configured to read thedata out of a modulated reflected-wave signal supplied from thereflector. Receiving a non-modulated carrier from the reflected-wavereader, the reflector modulates the received reflected wave by switchingbetween antenna load impedances for example, thereby superimposing dataon the non-modulated carrier. The reflected-wave reader receives thismodulated reflected wave to demodulate and decode the received modulatedreflected wave, thereby obtaining transmission data.

Configuring an antenna load impedance switch with a GaAs IC allows ahigh-speed switching operation with low power dissipation, which issmaller than about several 10 μW. This configuration can also realizehigh-speed data transmission in a high frequency band of 2.4 GHz (microwave).

Although the transponder can obtain electrical power by rectifying acarrier transmitted by the reader/writer 300, the electrical power thusobtained is insufficient for the transmission of large amounts of dataat high speeds. Namely, the transponder need not the electrical powerfor generating a carrier at the time of transmission. However, anelectrical power necessary for executing a transmitting operation formodulating a reflected wave and a receiving operation for demodulatingand decoding a modulated signal from the reader/writer 300 is suppliedfrom the host device 120.

FIG. 2 shows an exemplary internal configuration of the memory card 100in which a transponder is built. The memory card 100 shown has a flashmemory 103 making up a storage block, a terminal section 101, amemory/communications control section 102, a radio section 104, and anantenna 105.

A contact portion of the terminal section 101 is exposed outside, beingconnectible with the host device 120 as with an ordinary memory card.The flash memory 103 is able to store data in an electrically rewritablemanner. The memory/communications control section 102 transfers databetween the host device 120 and the flash memory 103 via the terminalsection 101 and transmits data of the memory/communications controlsection 102 to the reader/writer 300 via the radio section 104 and theantenna 105 in the form of reflected waves. The radio section 104 isequivalent to a transponder in a noncontact communications system.

FIG. 3 shows an exemplary internal configuration of the radio section104 in the memory card 100 shown in FIG. 2. The radio section 104 shown,equivalent to a transponder in a noncontact system, can operate here asa reflector in reflected-wave transmission.

Reference numeral 200 denotes an antenna switch of an SPDT (SinglePole/Double Throw) switch, which also switches between reflected-wavegeneration and transmission/reception. In the figure, terminal c isconnected to the antenna 105 in the memory card 100. The antenna switch200 is configured by a GaAs IC, for example, separate from another CMOScircuit module.

When transmission is made from the radio section 104, terminal b isturned off by a control signal (TX/RX) from a baseband control section(not shown). Next, transmission data (TX_DATA) is applied to terminal afrom the baseband control section. As shown in the figure, becauseterminal d of the antenna switch 200 is grounded, if the transmissiondata is “1”, the terminal of the antenna 105 is short-circuited. If thetransmission data is “0”, the terminal of the antenna 105 is opened.Thus, on the basis of a bit image of transmission data, the switching ofthe antenna switch 200 (namely, the switching of the terminal of theantenna 105) phase-modulates a non-modulated carrier received from theantenna 105, the phase-modulated carrier being radiated from the antenna105 as a modulated reflected-wave signal.

On the other hand, at the time of reception by the radio section 104,terminal b is kept on by the baseband control section, not shown.Therefore, an ASK (Amplitude Shift Keying) modulated signal received atthe antenna 105 is transmitted to an ASK reception block 201 viaterminal e to be demodulated into reception data (RX_DATA). Thus, thereception data is passed to the baseband control section, not shown.

FIG. 4 schematically shows an exemplary internal configuration of thereader/writer 300 as a reflected-wave reader with which the radiosection 104 shown in FIG. 3 makes communication. The reader/writer 300shown has an antenna 301, a circulator 302, a reception section 303, atransmission section 304, and a baseband control section 305.

The transmission section 304 generates a non-modulated carrier asinstructed by the baseband control section 305. The non-modulatedcarrier is radiated toward the radio section 104 from the antenna 301via the circulator 302. The circulator 302 is used to separate thetransmission wave from the reception wave when transmission andreception are executed at the same time.

As described above, the radio section 104 generates a reflected wave forthe non-modulated carrier from the reader/writer 300, the reflected wavebeing phase modulated in accordance with read data, so that thereflected wave is returned to the reader/writer 300 as a modulatedreflected wave. Being received by the reception section 303 via theantenna 301 and the circulator 302, this modulated reflected wave isconverted into a baseband IQ signal made up of in-phase (I) andquadrature (Q) thereof to be demodulated in the baseband control section305.

In transmitting data and a control command from the reader/writer 300 tothe radio section 104, the transmission section 304 generates an ASKmodulated wave in accordance with transmission data from the basebandcontrol section 305, the generated ASK modulated wave being radiatedfrom the antenna 301.

The baseband control section 305 has an interface for other devices.This interface can decode read image data and supply the decoded imagedata to a television set, not shown, as a video signal to be displayedor to a PC, not shown, connected via USB (Universal Serial Bus).

In the present embodiment, it is assumed that the service entry sequenceshown in FIGS. 9 and 10 be applied to the communications control betweenthe transponder and the reader/writer 300. Namely, the reader/writer 300transmits a beacon frame to tell a service area of the reader/writer 300and the transponder returns an entry frame within a predetermined entryperiod in response, upon which the connection between the reader/writer300 and the transponder is established via a connection request and aconnection response sequence.

It is not necessary for the reader/writer 300 to always keeptransmitting a beacon frame at a certain time interval. However, whenthe reading of information from the transponder becomes necessary (to bemore specific, every time an application for reading/writing data withthe transponder is started up), the reader/writer 300 starts a beacontransmitting operation. For example, the reader/writer 300 transmits abeacon frame every 10 to 100 millisecond.

Also, in the present embodiment, when the reader/writer 300 starts up anapplication for reading/writing information with the transponder, thereader/writer 300 sets a service permission level suitable for thatapplication (or the type of the application) and writes the servicepermission level to the beacon frame. In response, having received thebeacon frame, the transponder interprets the contents of the receivedbeacon frame and determines the accessibility by the reader/writerdepending on whether the received signal level of this beacon frame isat the service permission level.

Here, it is assumed that the reader/writer transmit a beacon frame at acertain transmission power and the transponder receive the beacon framebasically by direct wave (line-of-sight communication), the receivedsignal level at the transponder side being proportional to thecommunication distance with the reader/writer.

For example, having started up an application for executing datacommunication of high security, the reader/writer 300 sets a higherservice permission level to transmit a beacon frame. In response, if thebeacon received signal level is high, or only if the reader/writer 300is located in the proximity, the transponder permits access by thereader/writer 300, so that the interception by nearby communicationsterminals can be prevented.

On the other hand, if the reader/writer 300 has started up anapplication for executing data communication, such as image or audiodata requiring low security, there is little need for caring aboutinterception. Therefore, the reader/writer 300 sets a low servicepermission level to transmit a beacon frame and, in response, thetransponder permits access by the reader/writer 300 when the beaconreceived signal level is low, or the communication distance with thereader/writer 300 is comparatively long, so that the user need not bringthe reader/writer 300 and the transponder closest to each other, therebyenhancing the ease of use.

FIG. 5 shows a frame format of a beacon signal that is used in thecommunications system according to an embodiment.

A beacon frame 500 is made up of elements of information, such as apreamble 501, a unique word 502, an ID 503 of reader, a servicepermission level 504, notification information 505, and an errorverification code (CRC) 506.

The preamble 501 is used for bit (symbol) synchronization to be executedat demodulation. The unique word 502 is indicative of a data startposition. The ID 503 is an identifier uniquely assigned to every reader.The notification information 505 stores communication-associatedparameters and service information. A beacon period is also stored inthe notification information 505. The error verification code (CRC) 506is a CRC (Cyclic Redundancy Code) parity assigned to the data from theID 503 to the notification information 505 of every beacon frame.

The service permission level 504 is an information element newly addedto the present embodiment in order for the reader/writer 300 to controla communicable area corresponding to every application. The servicepermission level 504 is indicative how high the reception level of abeacon signal from the reader/writer 300 should be.

For example, assume that 60 [dBμV] be displayed as the servicepermission level 504. In this case, if a beacon signal is received fromthe reader/writer 300 at 50 [dB μV], the transponder cannot request thereader/writer 300 for connection. If a beacon signal is received fromthe reader/writer 300 at 65 [dBμV], the transponder can transmit aconnection request signal to the reader/writer 300.

Therefore, having started up an application for executing datacommunication of high security, the reader/writer 300 sets the servicepermission level 504 at a high level to transmit a beacon frame. Inresponse, the transponder operates to permit access by the reader/writer300 only when the reader/writer 300 is in the proximity, therebypreventing the interception by nearby communications terminals.

On the other hand, when the reader/writer 300 has started up anapplication for executing data communication of image or audio data oflow security, there is little necessity for taking the interception intoconsideration, so that the reader/writer 300 sets the service permissionlevel to a low level to transmit a beacon frame. In this case, if thecommunications distance is comparatively long, the transponder permitsthe access by the reader/writer 300, so that the user need not bring thecommunications devices closest to each other, thereby enhancing the easeof use.

In accordance with the service permission level 504 in the receivedbeacon frame, the transponder controls the access by the reader/writer300 depending on the received signal strength of the received beacon (oranother frame received from the reader/writer 300).

Hence, the radio section 104 in the transponder has means of measuringRSSI (Receiving Signal Strength Indicator). In the basis of a result ofRSSI measurement, the memory/communications control section 102determines whether to transmit a connection request frame to thereader/writer 300 (or whether to return a connection response frame inresponse to the connection request frame received from the reader/writer300).

FIG. 6 shows an exemplary configuration of the radio section 104 havingthe means of transmitting RSSI measurement results to thememory/communications control section 102. A difference between theconfiguration shown in FIG. 6 from that shown in FIG. 3 lies in that theASK reception block 201 is provided with the means of transmitting RSSIto the memory/communications control section 102. The measurement ofreception level is easy because ASK reception is executed originally.

FIG. 7 shows an exemplary communications sequence that is executedbetween the transponder and the reader/writer 300 in the communicationssystem according to the embodiment. It should be noted that, althoughnot shown in the figure, the transponder is assumed to return an entryframe in response to a beacon frame transmitted from the reader/writer300. Also, when the transponder transmits a connection request signal orother signals, it is assumed that a non-modulated carrier be suppliedfrom the reader/writer 300 in advance.

Having received the beacon frame 400, the transponder reads and storesthe service permission level 504 contained in the beacon frame 400.Further, the transponder measures the reception level of the beaconframe 400 (601) to determine whether the reception level is higher thanthe service permission level (602).

If the reception level is found to be higher than the service permissionlevel 504, then the transponder transmits, to the reader/writer 300, theconnection request frame 401 as a modulated reflected-wave signal inresponse to the non-modulated carrier received from the reader/writer300.

In response, having received the connection request signal 401 from thetransponder, the reader/writer 300 returns a connection response frame402 to the transponder. This establishes connection between thetransponder and the reader/writer 300, thereby putting thecommunications system into the communication state 403.

While embodiments have been described using specific terms, suchdescription is for illustrative purpose only.

In the description hereof made so far, the embodiment applied tocommunications systems configured to execute reflected-wave transmissionhas been mainly described. However, the embodiments not limited thereto.For example, even with communications systems employing anothercommunications scheme in which the transponder having no radio wavegenerating source of its own executes a data transmitting operation,such as electrostatic coupling or electromagnetic induction, theembodiments are applicable in the same manner in a situation where thereader/writer need to control the communicable area with the transponderfor every application. Alternatively, the present embodiments areapplicable in the same manner to communications systems in which boththe transmitting and receiving communications devices have radio wavegenerating sources of their own.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A first apparatus comprising: acommunication circuit which is configured to communicate with a secondapparatus; and a controller which is configured to control the firstapparatus to: receive, from the second apparatus, a beacon frameincluding service information; and transmit, to the second apparatus, aservice entry associated with the service information.
 2. The firstapparatus of claim 1, wherein the service entry is transmitted to thesecond apparatus for activating the service.
 3. The first apparatus ofclaim 1, wherein the beacon frame further includes service permissioninformation.
 4. The first apparatus of claim 3, wherein the servicepermission information indicates a signal level for permitting serviceactivation.
 5. The first apparatus of claim 4, wherein the controller isfurther configured to control the first apparatus to determine whetherthe service entry should be transmitted based on a received signalstrength and the service permission information.
 6. The first apparatusof claim 5, wherein the service entry is a connection request toestablish a connection with the second apparatus.
 7. The first apparatusof claim 6, wherein the controller is further configured to controltransmitting a communication parameter with the connection request. 8.The first apparatus of claim 1, wherein the controller determineswhether the service entry should be transmitted.
 9. A second apparatuscomprising: a communication circuit which is configured to communicatewith a first apparatus; and a controller which is configured to controlthe second apparatus to: transmit, to the first apparatus, a beaconframe including service information at a predetermined time interval;and receive, from the first apparatus, a service entry associated withthe service information.
 10. The second apparatus of claim 9, whereinthe controller activates the service when the second apparatus receivesthe service entry.
 11. The second apparatus of claim 9, wherein theservice entry is transmitted from the first apparatus.
 12. The secondapparatus of claim 9, wherein the beacon frame further includes servicepermission information which is used for a determination whether theservice entry should be transmitted.
 13. The second apparatus of claim12, wherein the service permission information indicates a signal levelfor permitting service activation.
 14. The second apparatus of claim 13,wherein the controller causes a communication with the first apparatuswhen the second apparatus receives the service entry.
 15. The secondapparatus of claim 14, wherein the service entry is a connection requestfrom the first apparatus and the controller is further configured tocontrol the second apparatus to control transmitting a connectionresponse to establish a connection with the first apparatus.
 16. Thesecond apparatus of claim 14, wherein the beacon frame includescommunication-associated parameters.
 17. The second apparatus of claim16, wherein the communication operates with the receivedcommunication-associated parameters.
 18. The second apparatus of claim9, wherein the beacon frame includes communication-associatedparameters.
 19. The second apparatus of claim 9, further comprising:after transmitting the beacon frame, transmit a non-modulated carriercontinuously during an entry period.
 20. A method for communicatingbetween a first apparatus and a second apparatus, the method comprising:receiving, from the second apparatus, a beacon frame including serviceinformation; and transmitting, to the second apparatus, a service entryassociated with the service information.
 21. A method for communicatingbetween a first apparatus and a second apparatus, the method comprising:transmitting, to the first apparatus, a beacon frame including serviceinformation at a predetermined time interval; and receiving, from thefirst apparatus, a service entry associated with the serviceinformation.
 22. A computer readable medium storing instructions forcommunicating between a first apparatus and a second apparatus which,when executed, cause the first apparatus to: receive, from the secondapparatus, a beacon frame including service information; and transmit,to the second apparatus, a service entry associated with the serviceinformation.
 23. A computer readable medium storing instructions forcommunicating between a first apparatus and a second apparatus which,when executed, cause the second apparatus to: transmit, to the firstapparatus, a beacon frame including service information at apredetermined time interval; and receive, from the first apparatus, aservice entry associated with the service information.